Sound translating apparatus



March 26, 1940. E. SCHULLER SOUND TRANSLATING APPARATUS Filed Aug. 50, 1939 Patented Mar. 26, 1940 SOUND TRANSLATING APPARATUS Eduard Schiiller, assignor to Gesellschaft, Berlin, Germany Application August so, 1939, In Germany Novemb 7 Claims.

This invention relates to sound translating apparatus and particularly to electromagnetic devices for recording sound on or reproducing sound from magnetic bands.

I The method of longitudinally magnetizingthe record carrier by superimposing a polarizing field upon the alternating field due to the signal current limits the amplitude of the sound record to about one-half the straight line portion of the magnetizing curve. high ratio of noise level to average signal level and, to obtain a higher signal or recording level, it has been proposed to act on difierent parts of the record carrier with two equal strength fields displaced in phase 180 relative to each other, thus producing two separate sound tracks. In the reproduction, the components from the separate sound tracks are combined in proper phase to form a single alternating current that is fed to the reproducing amplifier. The electromagnetic recorder and reproducer heads for use in the double sound track systems have been complicated and bulky, andit has been exceedingly diflicult to obtain a proper mechanical adjust,- ment of the components of either the recorder or the reproducer head to bring the slots of the magnetic cores into line. Lack of alinement oi the slots of the recorder head results in faulty reproduction when the older types of reproducer heads are used and,'in the case of a reproducer head having separate electromagnets' for each sound track, distortion is present when the slots of the reproducer head are not out of alinement to the same extent as the slots of the recorder head. I

An object of this invention is to provide electromagnetic devices of simple design for use as recorder or reproducer heads'in magnetic sound translating systems. An object is to provide an electromagnetic head of the type stated which includes two cores of identical design that are reversely arranged and. firmly connected to each other with their air gaps in exact alinement. An object is to provide an electromagnetic head including two cores that are each formed two non-identical parts,'the unlike parts of the two cores being rigidly secured to each other so that, upon reversely joining the two assemblies, the air gaps of the two cores are exactly alined. A furinvention will be apparent from the following This results in a relatively ther object is to provide an electromagnetic head- Berlin-Johan'nisthal, Germany, Licentia Yatent-Verwaltungs- Serial No. 292,741 er 23, 1938 specification when taken with the accompanying drawing in which:

Fig. 1 is a perspective view of an electromagnetic head embodying the invention; and

Fig. 2 is an exploded perspective view of the 5 same.

As shown in the drawing, the two cores of a recorder or reproducer head are of approximately semi-circular or D-shape and their component parts I, 2

and 3, 4 are reversely arranged. A

screening plate 5 of'non-magnetic material is located between the cores to separate the magnetic fields from each other, and this assembly is mounted between heavy clamping plates 6, I and held. in fixed position by screws through the plate 9 of the plate 1. The upper ends v the cores are spaced to providenarrow air gaps 8 that extend l5 6 and are threaded into bores of the parts of III, II respectively, across which the record carrier travel s,'and, as shown, the lower ends may be spaced to leave air gaps I2, l3, respectively.

Thewin dings ll, 15 may be placed on one part of each core, for example the curved parts 2 and 4, respectively, or may include sections on each core part.

The D-shape and reversed arrangement of the cores provide ample space for the windings without unduly enlarging the complete sound translating head assembly.

The assembled head may sound recording and reproducing apparatus in be mounted in the.

any desired manner. It is convenient to provide screws I! in the clamping plates 6, 1, or

The great advantage of the described construction is in the mechanical design that permits the simultaneous machining or grinding of parts of ,the cores. The straight section I of the outer core (as seen in Fig. 1) and the curved section l in Fig. 1, core sectio of the inner core are firmly united by cementing, 40

welding or riveting, and core sections 2, 3 is the other set of unlike similarly united. As shown rivets l8 extend through each set of us to form a rigid assembly that can be worked as a unit. The upper end of one unit assembly terminates in polar surfaces at one side of the air gaps l0, H; and the upper end of the other unit assembly provides the opposed polar surfaces.

with high accuracy two units, alinement extending Similarly, core parts These polar surfaces may be ground and, upon assembling the the gaps l0 and il will be in exact to form, in effect, a common air gap transversely of the core assembly. the lower ends of the united pairs of may be accurately machined for exact mating or, as shown, to provide a second air gap that is common to the cores.

The invention is not limited to the exact construction herein shown and described as the relative shape and size of the parts may be varied without departing from the spirit of my invention as set forth in the following claims.

I claim:

1. A sound translating head for use with a magnetic record carrier of the double sound track type, said head comprising a pair of magnetic cores each including two parts terminating in polar surfaces that are spaced from each other to provide an air gap across which the record carrier is to travel, a winding on each core, and means securing the cores to each other with their air gaps in alinement; said securing means comprising means rigidlyconnecting in pairs the parts of the two cores at each side of the air gap, and means securing the pairs of core parts in fixed relation to each other.

2. A sound translating head for use with a magnetic record carrier of the double sound track type, said head comprising a pair of cores of approximately semicircular shape and each including two parts terminating in polar surfaces that are spaced from each other to provide an air gap across which the record carrier is to travel, a Winding on at least one part of each core, means rigidly securing a part of one core to a part of the other core with the polar surfaces of the parts in alinement, means rigidly securing the other pair of core parts to each other with their polar surfaces in alinement, and means mounting the pairs of core parts in fixed position with respect to each other.

3. A sound translating head as claimed in claim 2, wherein the parts of each core are approximately straight and curved, respectively.

4. A sound translating head as claimed in claim 2, wherein the parts of each core are approximately straight and curved, respectively, and correspondingly shaped parts of the two cores are reversely arranged with respect to the alined air gaps of the cores.

5. A sound translating head as claimed in claim 2, wherein the united pairs of pole parts are spaced apart at their ends opposite to said polar surfaces to provide a second air gap in each core.

6. A sound translating head as claimed in claim 2, in combination with a screening plate of nonmagnetic material between said cores.

7. A sound translating head as claimed in claim 2, wherein said mounting means comprises clamping plates at opposite sides of said cores that fit the shape of the cores.

EDUARD SCHULLER. 

